RE: st: Understanding Factor variables - is order significant ?

I'm very happy with for the first (out of uncountable occasions) Stata
is wrong !!!!
Do you get a "find a bug" T-shirt ;-)
I'm looking forward to a fix as I find the factor variable feature
extremely useful.
Jesper
Jesper Lindhardsen
MD, Ph.d. student
Department of Cardiovascular Research
Copenhagen University Hospital, Gentofte
Denmark
-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Richard
Williams
Sent: 27. maj 2010 00:45
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: Understanding Factor variables - is order significant ?
You wonder how such an obvious problem could be missed. :) Actually,
I think this should be a strong contender for most esoteric bug of
the year award! Thanks for fixing it.
At 03:17 PM 5/26/2010, Roberto G. Gutierrez, StataCorp wrote:
>Jesper (and those others who have contributed on this thread) have
discovered
>a bug in how factor-variable interactions are being parsed in Stata.
The
>specific conditions that trigger this are as follows:
>
> 1. You specify a simple interaction (a single # sign) between two
or more
> factor variables.
>
> 2. The first variable in the interaction has the value zero as one
of
> its categories.
>
> 3. The first specification in the interaction has a base level that
is
> not the default of zero (the lowest level for the first
variable).
>
> 4. At least one of the remaining variables in the interaction has a
base
> equal to the lowest-valued category for that variable,
> whether expicitly
> specified or taken as the default.
>
> 5. Almost all estimation commands are affected by this bug, with
-regress-
> being one notable exception.
>
>When the above conditions occur, Stata is attempting to omit an extra
cell in
>the interaction. Sometimes, the cell will be omitted altogether, other
times
>Stata will produce a coefficient for that cell, but missing standard
errors
>and confidence intervals. Either way, the model fit is thrown off
because the
>cell's coefficient is not properly estimated.
>
>We will fix this in the next executable update, to be made available
soon.
>
>--Bobby --Jeff
>rgutierrez@stata.com jpitblado@stata.com
>*
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-------------------------------------------
Richard Williams, Notre Dame Dept of Sociology
OFFICE: (574)631-6668, (574)631-6463
HOME: (574)289-5227
EMAIL: Richard.A.Williams.5@ND.Edu
WWW: http://www.nd.edu/~rwilliam
*
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*
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* http://www.ats.ucla.edu/stat/stata/